The search for non-genetic risk factors for amyotrophic lateral sclerosis (ALS) has progressed slowly over the past decades. Although numerous hypotheses have been proposed, outside of age and male gender, no risk factor has emerged as a consistent and accepted predictor of risk. The lack of rigorous population based studies of ALS with prospectively collected exposure data has probably been one of the causes. We propose here to study the relations between prospectively collected data on veteran status, occupation, occupational exposure to lead, race and ethnicity, education, and cigarette smoking and risk of ALS in the National Longitudinal Mortality Study (NLMS). The NLMS is a cohort study of almost 2.4 million men and women who completed the Current Population Survey (CPS) of the US Bureau of the Census between 1973 and 2002, which collected a variety of data, including extensive socioeconomic data, that allows us to explore our specific variables of interest while controlling for possible confounding by a variety of factors that could themselves be related to risk of ALS. The selection of these participants was done to achieve representation of the US non- institutionalized population and the response rate was greater than 96%. Follow up of the cohort for causes of mortality via linkage with the National Death Index is complete through 1998, almost complete through 2002, and we propose to extend this follow-up for a portion of NLMS participants through 2013. We have identified 713 deaths from ALS, which, even as a minimum of the eventual total we will have, makes this study not only one of the largest of the few cohort studies with prospectively collected data, but also the only one that is representative of the US population.